The present invention relates to a blood sampling device that incorporates a lancet assembly for piercing the skin, and more particularly to a blood sampling device having a particular type of lancet holder for holding the lancet assembly.
A conventional blood sampling device has a lancet assembly in the form of a generally cylindrical plastic body in which a needle-like lancet is disposed. A portion of the plastic body has a number of outwardly extending ribs disposed thereon. A conventional lancet assembly is shown, for example, in FIG. 6 of U.S. Pat. No. 4,976,724 to Nieto, et al. The lancet assembly is held within a generally cup-shaped lancet holder by an interference fit. The lancet holder is typically disposed within a housing along with an actuator mechanism for moving the lancet holder between a cocked position, a puncture position, and a resting position intermediate the cocked and puncture positions.
A conventional lancet assembly also includes a plastic protective cap that covers the sharp tip of the lancet to prevent inadvertent skin puncture prior to use of the blood sampling device. When a blood sample is to be taken, the lancet assembly is forced into the cylindrical opening formed in the cup-shaped lancet holder, and the protective cap is twisted off the lancet assembly so that the tip of the lancet is exposed. To prevent the lancet assembly from turning within the lancet holder when the protective cap is twisted off (the interference fit is typically not strong enough to prevent such turning), the interior of a conventional, industry standard lancet holder is provided with a plurality of angularly spaced ribs which prevent rotation of the lancet assembly by making contact with the outwardly extending ridges of the lancet body. Although such ribs are useful in preventing unintended rotation of the lancet assembly relative to the lancet holder when the protective cap is twisted off, they may hinder the insertion of the lancet assembly into the lancet holder if the lancet assembly is not properly oriented relative to the lancet holder. This may cause frustration to the user of the blood sampling device and/or improper seating of the lancet assembly within the lancet holder.
U.S. Pat. No. 4,442,836 to Meinecke, et al. discloses a blood lancet device having a lancet holder of the type described above which is adapted to be inserted into a lancet holder having a hexahedral-shaped aperture with a square cross-section, as shown in FIG. 6 of the patent. The Nieto, et al. patent referred to above discloses a blood sampling device in which a lancet assembly having a protective cap is inserted into a collar-shaped lancet-holding mechanism having a tubular chamber, with an interference fit between the lancet assembly and the lancet holding mechanism.